An organic solar cell is a device that can directly convert solar energy into electric energy by applying a photoelectromotive effect. The solar cell may be divided into an inorganic solar cell and an organic solar cell according to a material constituting a thin film. A typical solar cell is manufactured by doping crystalline silicon (Si) that is an inorganic semiconductor to perform p-n conjunction. Electrons and holes generated by absorbing light are diffused to a p-n conjunction point, and are accelerated by an electric field thereof to move to an electrode. Electric power conversion efficiency of this process is defined by a ratio of electric power provided to an external circuit and solar power provided to the solar cell, and recently, has attained to about 24% when measured under a standardized virtual solar radiation condition. However, since an existing inorganic solar cell already has limitations in view of economic feasibility and supply and demand on materials, an organic semiconductor solar cell that is easily processed, at low cost, and includes various functionalities has come into the limelight as a long-term alternative energy source.
In the solar cell, it is important to increase efficiency so as to outadded as much electric energy as possible from solar energy. In order to increase efficiency of the solar cell, it is important to generate as many excitons as possible in a semiconductor, and also important to draw generated electric charges to the outside without a loss. One of the factors of the electric charge loss is extinction caused by recombination of the generated electrons and holes. Various methods have been proposed as a method for transporting the generated electrons or holes to an electrode without a loss, but most methods require an additional process, and thus manufacturing cost may be increased.